Internet Engineering Task Force (IETF) T. Bray, Ed. Request for Comments: 8259 Textuality Obsoletes: 7159 December 2017 Category: Standards Track ISSN: 2070-1721 Internet Engineering Task Force (IETF) T. Bray, Ed. Request for Comments: 8259 Textuality Obsoletes: 7159 December 2017 Category: Standards Track ISSN: 2070-1721 This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Conventions Used in This Document . . . . . . . . . . . . 4 1.2. Specifications of JSON . . . . . . . . . . . . . . . . . 4 1.3. Introduction to This Revision . . . . . . . . . . . . . . 5 2. JSON Grammar . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Values . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6. Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 7. Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8. String and Character Issues . . . . . . . . . . . . . . . . . 9 8.1. Character Encoding . . . . . . . . . . . . . . . . . . . 9 8.2. Unicode Characters . . . . . . . . . . . . . . . . . . . 10 8.3. String Comparison . . . . . . . . . . . . . . . . . . . . 10 9. Parsers . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 10. Generators . . . . . . . . . . . . . . . . . . . . . . . . . 10 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 12. Security Considerations . . . . . . . . . . . . . . . . . . . 12 13. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 12 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 14.1. Normative References . . . . . . . . . . . . . . . . . . 14 14.2. Informative References . . . . . . . . . . . . . . . . . 14 Appendix A. Changes from RFC 7159 . . . . . . . . . . . . . . . 16 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Conventions Used in This Document . . . . . . . . . . . . 4 1.2. Specifications of JSON . . . . . . . . . . . . . . . . . 4 1.3. Introduction to This Revision . . . . . . . . . . . . . . 5 2. JSON Grammar . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Values . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6. Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 7. Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8. String and Character Issues . . . . . . . . . . . . . . . . . 9 8.1. Character Encoding . . . . . . . . . . . . . . . . . . . 9 8.2. Unicode Characters . . . . . . . . . . . . . . . . . . . 10 8.3. String Comparison . . . . . . . . . . . . . . . . . . . . 10 9. Parsers . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 10. Generators . . . . . . . . . . . . . . . . . . . . . . . . . 10 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 12. Security Considerations . . . . . . . . . . . . . . . . . . . 12 13. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 12 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 14.1. Normative References . . . . . . . . . . . . . . . . . . 14 14.2. Informative References . . . . . . . . . . . . . . . . . 14 Appendix A. Changes from RFC 7159 . . . . . . . . . . . . . . . 16 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16 The reference to ECMA-404 in the previous sentence is normative, not with the usual meaning that implementors need to consult it in order to understand this document, but to emphasize that there are no inconsistencies in the definition of the term "JSON text" in any of its specifications. Note, however, that ECMA-404 allows several practices that this specification recommends avoiding in the interests of maximal interoperability. A JSON text is a serialized value. Note that certain previous specifications of JSON constrained a JSON text to be an object or an array. Implementations that generate only objects or arrays where a JSON text is called for will be interoperable in the sense that all implementations will accept these as conforming JSON texts. %x20 / ; Space %x09 / ; Horizontal tab %x0A / ; Line feed or New line %x0D ) ; Carriage return %x20 / ; Space %x09 / ; Horizontal tab %x0A / ; Line feed or New line %x0D ) ; Carriage return An object structure is represented as a pair of curly brackets surrounding zero or more name/value pairs (or members). A name is a string. A single colon comes after each name, separating the name from the value. A single comma separates a value from a following name. The names within an object SHOULD be unique. An object whose names are all unique is interoperable in the sense that all software implementations receiving that object will agree on the name-value mappings. When the names within an object are not unique, the behavior of software that receives such an object is unpredictable. Many implementations report the last name/value pair only. Other implementations report an error or fail to parse the The representation of numbers is similar to that used in most programming languages. A number is represented in base 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. This specification allows implementations to set limits on the range and precision of numbers accepted. Since software that implements IEEE 754 binary64 (double precision) numbers [IEEE754] is generally available and widely used, good interoperability can be achieved by implementations that expect no more precision or range than these provide, in the sense that implementations will approximate JSON numbers within the expected precision. A JSON number such as 1E400 or 3.141592653589793238462643383279 may indicate potential interoperability problems, since it suggests that the software that created it expects receiving software to have greater capabilities for numeric magnitude and precision than is widely available. The representation of strings is similar to conventions used in the C family of programming languages. A string begins and ends with quotation marks. All Unicode characters may be placed within the quotation marks, except for the characters that MUST be escaped: quotation mark, reverse solidus, and the control characters (U+0000 through U+001F). Any character may be escaped. If the character is in the Basic Multilingual Plane (U+0000 through U+FFFF), then it may be represented as a six-character sequence: a reverse solidus, followed by the lowercase letter u, followed by four hexadecimal digits that encode the character's code point. The hexadecimal letters A through F can be uppercase or lowercase. So, for example, a string containing only a single reverse solidus character may be represented as "\u005C". escape ( %x22 / ; " quotation mark U+0022 %x5C / ; \ reverse solidus U+005C %x2F / ; / solidus U+002F %x62 / ; b backspace U+0008 %x66 / ; f form feed U+000C %x6E / ; n line feed U+000A %x72 / ; r carriage return U+000D %x74 / ; t tab U+0009 %x75 4HEXDIG ) ; uXXXX U+XXXX escape ( %x22 / ; " quotation mark U+0022 %x5C / ; \ reverse solidus U+005C %x2F / ; / solidus U+002F %x62 / ; b backspace U+0008 %x66 / ; f form feed U+000C %x6E / ; n line feed U+000A %x72 / ; r carriage return U+000D %x74 / ; t tab U+0009 %x75 4HEXDIG ) ; uXXXX U+XXXX However, the ABNF in this specification allows member names and string values to contain bit sequences that cannot encode Unicode characters; for example, "\uDEAD" (a single unpaired UTF-16 surrogate). Instances of this have been observed, for example, when a library truncates a UTF-16 string without checking whether the truncation split a surrogate pair. The behavior of software that receives JSON texts containing such values is unpredictable; for example, implementations might return different values for the length of a string value or even suffer fatal runtime exceptions. Software implementations are typically required to test names of object members for equality. Implementations that transform the textual representation into sequences of Unicode code units and then perform the comparison numerically, code unit by code unit, are interoperable in the sense that implementations will agree in all cases on equality or inequality of two strings. For example, implementations that compare strings with escaped characters unconverted may incorrectly find that "a\\b" and "a\u005Cb" are not equal. Applications that use this media type: JSON has been used to exchange data between applications written in all of these programming languages: ActionScript, C, C#, Clojure, ColdFusion, Common Lisp, E, Erlang, Go, Java, JavaScript, Lua, Objective CAML, Perl, PHP, Python, Rebol, Ruby, Scala, and Scheme. Since JSON's syntax is borrowed from JavaScript, it is possible to use that language's "eval()" function to parse most JSON texts (but not all; certain characters such as U+2028 LINE SEPARATOR and U+2029 PARAGRAPH SEPARATOR are legal in JSON but not JavaScript). This generally constitutes an unacceptable security risk, since the text could contain executable code along with data declarations. The same consideration applies to the use of eval()-like functions in any other programming language in which JSON texts conform to that language's syntax. "Title": "View from 15th Floor", "Thumbnail": { "Url": "http://www.example.com/image/481989943", "Height": 125, "Width": 100 "Animated" : false, "IDs": [116, 943, 234, 38793] "Title": "View from 15th Floor", "Thumbnail": { "Url": "http://www.example.com/image/481989943", "Height": 125, "Width": 100 "Animated" : false, "IDs": [116, 943, 234, 38793]